Fluid actuator



July 1963 w. 1.. CARLSON, JR 3,099,136

FLUID ACTUATOR 2 Sheets-Sheet 1 Original Filed May 19, 1960 PUMPINVENTOR. WlLLlAM L. CARLSON, JR.

ATTORNEY July 30, 1963 w, CARLSQN, JR 3,099,136

FLUID ACTUATOR Original Filed May 19, 1960 2 H 2 Sheets-Sheet 2INVENTOR.

WILLIAM L. CARLSON,JR.

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A TTORNE Y United States Patent 3,099,136 FLUKE) AUTUATOR William L.Carlson, In, loomington, Minn, assignor to Minneapolis-HoneywellRegulator Company, Minneapoils, Minn, a corporation of Delaware Originalapplication May 19, 1960, Ser. No. 39,211, new Patent No. 3,008,294,dated Nov. 14, 1961. Divided and this application Nov. 2, 1%1, Ser. No.149,677

6 tilaims. (61. 60-52) The present invention is broadly directed to anovel type of hydraulic actuator which is particularly adapted for usewith conductive fluids such as liquid metals. More specifically, thepresent actuator utilizes a double bellows sealed shaft and a dump valvethat allow the uni-t to operate rapidly on a return stroke without theimpedance of flow of the fluid through the pump that originally suppliesthe operating pressure to the actuator.

The present application is a division of my co pending applicationSerial No. 30,211 filed May 19, 1960, and now Patent Number 3,008,294issued November 14, 1961.

The use of conductive fluid pumps and actuators is progressivelybecoming more common and is typified by US. Patent No. 2,897,650 and theBritish Patent No. 810,697. Both of these patents are assigned to theassignee of the present invention and disclose the use ofelectromagnetic conductive fluid pumps with actuators that supplymechanical outputs whenever the conductive fluid pumps are energized,and which allow the conductive fluid to flow back hrough the openpassage of the conventional electromagnetic conductive fluid pumps ontheir return stroke. Actuators of this general type are generallysomewhat slow in returning due to the impedance to flow of theconductive fluid through the channel of an electromagnetic conductivefluid pump. In order to overcome this impedance, the present inventionis directed to a dump valve which operates on a pressure differential inthe actuator to allow for the pump .to be bypassed on the return stroke,thereby allowing for rapid return of the conductive fluid from apressure chamber of the actuator to a reservoir chamber of the actuator.Since this type or" unit utilizes a conductive fluid that normally mustbe hermetically sealed, the present invention is directed to a doublebellows sealing arrangement for the reservoir chamber that allows forthe rapid response of the unit without adding a separate reservoirchamber as might be needed otherwise.

In the present case, it is the primary object to disclose a dump valvearrangement which is pressure operated and does not rely on fluid flowas does the ordinary check valve or dump valve.

Another object of the present invention is to disclose a dump valve thatcan be made to operate on power failure to the conductive fluid pump andthereby acts as a safety control.

Yet another object of the present invention is to disclose a dump valvethat is subject to both pressure control and to selective electriccontrol for use in actuators where a modulation of the actuator isdeveloped by modulating the pressure input to the actuator from thepump.

Still a further object of the present invention is to disclose a dumpvalve that can be put into a hermetically sealed unit compatible withconductive fluid-s of the liquid metal type, such as sodium, potassium,or an alloy of sodium-potassium referred to as NaK, and which isexceedingly simple and reliable.

Yet a fiur-ther object of the present invention is to disclose a dumpvalve that is exceedingly inexpensive to build into an actuator.

3,099,136 Patented July 30, 1963 "ice Another object of the presentinvention is to disclose a hermetically sealed actuator that can be usedwith fluids of the corrosive type, as mentioned previously, and that hasa double bellows seal so that the reservoir chamber changes in volumereadily with operation of the pump and dump. valve.

In order to more fully understand the present invention, the inventionhas been disclosed schematically in FIGURE 1, wherein the dump valve isdisclosed;

FIGURE 2 is a similar schematic representation of the invention, butincludes an electrical means of operating the dump valve which is shownin the form of a solenoid; and,

FIGURE 3 is a cross section of a production version of an actuator ofthe type disclosed in FIGURE 1, with the additional feature of thedouble bellows seal on the output shaft.

Disclosed in FIGURE 1 is a pump 10, preferably an electromagneticconductive fluid pump having a continuously open fluid flow channel.This type of pump is sometimes referred to as a Faraday type pump and iswell known in the art. Electric current is supplied through conductors11 and 12 from any convenient power source. The pump 10' has an outlet13 schematically disclosed as supplying a conductive fluid to twoconduits or pipes 14 and 15. The pipe 14 passes into an actuatordisclosed at 16 to a pressure chamber or area 17. As will be seen in thefollowing description, actuator 16 includes a fluid chamber which isseparated into two smaller chambers or areas 17 and 35'. The pipe orconduit passes into a valve chamber means 20- that houses the novel dumpvalve that controls the actuator 16.

The dump valve includes a diaphragm 21 that ca ries a valve member 22against a valve seat 23. The valve member 22. is disclosed in its openposition which occurs when the pump 10 is deenergized. The diaphragm 21is sealed at its edge 24 to a plate 25 that forms part of the upper wallof chamber 17 and to valve seat 23. This plate has a number of openings26 that allow free communication of fluid from the pressure chamber 17to the underside of the diaphragm 21.

The valve seat 23 is connected to a pipe 3% that returns to the inlet 31of the pump 10. The upper part of the pressure chamber 17 has its wallssealed to the main Walls of the actuator 16 in a fluid tight manner,such as by welding. The pipe is sealed also in a fluid tight manner asit passes through the upper wall of the actuator.

With the arrangement described thus far, the actuator 16 has a pressurechamber 17 that communicates with the underside of the diaphragm 21. Theunderside of the diaphragm 21 and the fluid chamber are in communicationwith the pipe 30 through the valve seat 23 which, in turn, allows fluidflow to pass through the pipe 3d to the inlet of pump 1%. A secondchamber, that is, the valve chamber means 24), is completely sealed fromthe pressure chamber 17 and is in communication with the outlet of pump1!} through the pipe 15. In order to complete the chamber 17, a pistonmeans 32 is provided to separate the actuator 16 into the previouslymentioned two pressure chambers or areas. The piston means 32 has ashaft 33 that is used as output means for the actuator 16. A simplegasket 34 is shown as a sealing means around shaft 33 but it isunderstood that this is for simplicity in explanation of the operatingprinciples of the unit. A more practical seal is disclosed in FIGURE 3and will be described in detail in the discussion directed to thatfigure.

The piston means 32 provides a reservoir chamber or areas 35 bet-Weenthe piston means 32 and the side and bottom walls of the actuator 16. Apipe 36 is connected through a lower wall of the actuator 16 tocommunicate with the reservoir chamber 35. back to the inlet 31 of thepump direct communication between the reservoir chamber '35.

The operation of the device disclosed in FIGURE 1 can best be understoodby considering the pres-sure in chambers 17 and 35 as being equal whenthe pump is deenergized. At this time, the diaphragm 21 holds the valve22 off the valve seat 23 to allow a free communication of the fluid thatfills the chambers 17 and 35 along with all of the piping and pump 10.Upon application of power to conductors 11 and 12, the pump 10 creates apressure that forces the fluid filling the system out of the outlet 13into the conduits 14 and 15. The fluid flowing from outlet 13 throughthe conduits 14 and 15' supplies a fluid pressure to the pressurechamber 17 and to the valve chamber means 20. The conduits 14 and 15 arearranged so that a pressure drop occurs in the conduit 14, therebycreating a slightly lower pressure in the pressure chamber 17 thanoccurs in the valve chamber means 20. Since there is little or no flowinvolved in conduit 15, a larger pressure drop develops in conduit 14than in conduit 15 due to the frictional flow losses in conduit 14 andthis pressure drop moves the diaphragm 21 in a downward direction. Thediaphragm carries the valve 22 against the valve seat 23 whichimmediately seals the pressure chamber 17 and allows a pressure to buildup in the pressure chamber to apply a driving force against the pistonmeans 32. It will be understood that the full pump pressure is appliedto the diaphragm 21 at this point, whereas l3. slightly lower pressureis applied to the underside of diaphragm 21 from the pressure chamber 17via the holes 26. A difference in force across the diaphragm 21 occursdue to a difference in effective area-s created by the area of the valveseat 23 being removed from the effective area of the underside ofdiaphragm 21 due to valve 22 seating on seat 23.

With the pump pressure thus applied and the valve 22 seated againstvalve seat 23, the full pump pressure operates against the piston means32 to move the piston means 32 in a downward direction. The movement ofpiston means 32 downward decreases the volume of the reservoir chamber35, forcing fluid through conduit 36 into the inlet side 31 of pump 10.When the piston means 32 reaches the bottom of the actuator 16 oroperates against a load (not shown) that causes the piston means 32 tostall against the pumping pressure of pump 10', the unit will remain inequilibrium with the pump 10 supplying continuous pressure to hold thepiston means 32 in its downward position. Since the pump 10 is of theelectromagnetic conductive fluid type, stalling the pump creates noserious problem from a mechanical or electrical standpoint.

As soon as it is desired to return the piston means 32 in an upwarddirection, it is only necessary to deenergize the pump 10 by removingpower from conductors 1'1 and 12. The load (not shown) connected toshaft 33- is biased in an upward direction by a spring or other suitablemeans and causes the piston means 3-2 to want to move upward. Since thepump is deenergiz ed, pressure in chamber means goes to Zero whilepressure in pressure chamber 17 remains substantially constant since, asstated previously, shaft 33 and its attached piston 32 are biasedupwardly by means not shown. This allows the valve 22 to move slightlyoff the valve seat 23, and opens a direct communication between thepressure chamber 17 and the reservoir chamber 35 through the tube 30.The fluid in pressure chamber 17 is thus immediately dumped through tube30 into tube 36 and back to the reservoir chamber 35, thereby allowingthe piston means 32 to move in an upward direction unimpeded by thefluid passage through the pump 10 from the outlet 13 to the inlet 31.

It can thus be seen that a unique type of dump valve that is pressureoperated has been supplied to a hermeti- The pipe 36 connects 10 andalso provides a valve seat 23 and the cally sealed conductive fluidsystem and provides for a unique form of operation.

The device disclosed in FIGURE 1 has been modified in FIGURE 2 to add anelectric control for the system. This allows for modulation of the unitby pulsing or by varying the pumping pressure created by pump 10.Similar numbers will be utilized for similar parts, and the basic modeof operation of the device in FIGURE 2 is the same as that in FIGURE 1with the additional features described in detail. The pump 13 again isenergized through conductors 11 and 12 to provide a pumping pressure atoutlet 13 and through conduit 14 and conduit 15. For convenience inoperation, a check valve 40 has been inserted in conduit 14 and preventsfluid from returning to the outlet 13 of the pump during operation ofthe unit. The actuator 16 is divided by piston means 32 into a pres surechamber 17 and a reservoir chamber 35. The reservoir chamber isconnected by pipe 36 back to the inlet 31 of the pump and communicatesby pipe 30 with the valve seat 23. The valve seat 23 has a valve 22cooperating therewith and is carried by the diaphragm 21 which is sealedat 24 as was disclosed in FIGURE 1. Holes 26 again provide communicationbetween the pressure chamber 17 and the underside of the diaphragm 21 sothat the fluid pressure in chamber 17 can readily be communicated andpermits flow of the conductive fluid in the unit from the pressurechambar 17 to the pipe 30 upon opening of the valve 22.

A valve chamber means 41 is than the valve chamber means corporate asolenoid plunger column 43 that is connected and operates the valve 22provided which is larger 20 of FIGURE 1, to in- 42 that is supported bya to the top of the valve 22 under certain circumstances. Externallymounted to the valve chamber means 41 is a solenoid coil 44 that has apair of energizing leads 45 and 46 that can be connected to a suitablesource of power to energize the coil 44 and thereby create a magneticfield that is utilized to close the valve 22 against the valve seat 23during energization. The diaphragm 21 is so constructed as to provide aspring eflect that holds the valve 22 off the valve seat 23 even withthe additional weight of the solenoid plunger 42. If necessary, springmeans (not shown) could be added fior this purpose. The spring means(not shown) has been left 01f for clarity in disclosing the presentinvention.

In operation, the basic principles described in FIGURE 1 apply to FIGURE2. When the pump 10* is energized by supplying power to conductors 11and 12, a pressure is applied to the upper side of the diaphragm 21through the conduit 15 and the valve chamber means 41. Since the valve22 is off its valve seat 23, the fluid initially flowing from the outlet13 of the pump when it is first energized flows through the conduit 14into the pressure chamber 17 from where it flows through ports 26 intothe conduit or pipe 30. The pressure thus applied would normally causethe diaphragm 21 to move down and seal the valve seat 23 by applying thevalve 22. This action is immediately aided by energizing the conductors45' and 46 to supply power to the solenoid coil 44. This solenoid coilapplies a force to the plunger 42, thereby causing a definite and directseating of the valve 22 on valve seat 23, regardless of the pressures.With this arrange ment it should be understood that the pressure aloneon the unit may not be suflicient to operate the diaphragm valvedepending on the mode of operation of the unit. It will be noted that ifthe pump 10 is then deenergized but the solenoid coil 44 is keptenergized, the pressure in the pressure chamber 17 cannot be releasedsince the solenoid plunger 42 will hold the valve 22 closed against itsseat 23. The check valve 40 prevents reverse flow of the fluid from thechamber 17 to the pressure on the underside of the diaphragm 21increasing due to a movement in an upward direction of the piston means32.

With the arrangement disclosed in FIGURE 2, it is possible to obtainmodulation of the actuator 16 by utilizing either off-on operation or bymodulating the power to the pump 16. A definite power failure control isalso provided since the deenergization of the conductors 45 and 46 willcause the solenoid 44 to allow the solenoid plunger 42 to rise, therebydumping the valve upon power failure. With the combination of thepumping pressure and the pressure applied by the solenoi plunger 42, itis possible to operate the actuator 16 in various control functions thatwill be obvious to anyone working in the hydraulic and related arts.

In FIGURE 3, pump is energized through conductors 11 and 12 to supply afluid pressure at outlet 13 to pipes 14 and 15. Pipe 14 leads directlyinto the pressure chamber 17 of the actuator generally shown at 16. Thepipe leads into the valve chamber means 25 which has a flexiblediaphragm 21 that supports the valve member 22. The valve member 22cooperates with valve seat 23 which is formed in the dividing plate 25.Dividing plate 25 has a hole 26 that allows free communication of fluidfrom the pressure chamber 1 7 to the underside of the diaphragm 21. Thestructure described is substantially identical to the structureschematically represented in FIGURE 1.

The valve seat 23 opens onto a tube 30 which is con nected to a returntube 36 to the inlet 31 of the pump 10. In the more refined version ofFIGURE 3, the piston means 32 is formed of a piston-like member 56 thatis encapsulated in a rubber 51 that forms a tight but sliding seal at 52to the wall 53: of the actuator 16. Attached by any convenient method tothe top 54 of the piston 50 is a stem or shaft 33. Surrounding shaft 33is a spring 55 that extends to a stop member 56 that is joined at 57 tothe outer wall 60 of the actuator 16. The stop 56 acts as a guide forthe shaft 33 and also provides a mounting means to a plate 61 that canbe a separate mounting plate for the actuator 16 or an integral part ofa device to be controlled.

Surrounding the shaft 33 there is a bellows 62 that is attached at 63between the top of the shaft 33 and the piston top 54 so that thebellows 62 moves in compression whenever the shaft 33 is caused to movein a downward direction. The bellows 62 is sealed at 64 to a cuplikemember 65 that forms the lower end of a second concentric bellows 66.The second or concentric bellows is attached to the outer wall 68} ofthe actuator 16 at 67. The attachment of bellows 66 at 67 is such thatthe pipe 36 connects into the volume between the bellows 66 and 62 toform the reservoir chamber 35. The area between the bellows 66 and theouter wall 60 of the actuator 16 is utilized to assemble the unit and noform a protective wall for the thin bellows members that actually retainthe conductive fluid utilized in the present device.

In considering the operation of the device disclosed in FIGURE 3, itsoperation is identical to that of FIG- URE 1. This operation is thatupon energization of pump 16 fluid is caused to flow through pipes 14and 15. A pressure dilferential is developed between the pressurechamber 17 and the valve chamber means 24} to cause the valve member 22to lower against valve seat 23 to cut off a return path for the fluid.The return path would be from the pressure chamber 17 through opening 26through the valve seat 23, into tube 30, and back to the inlet 31 ofpump 10. As soon as valve 22 seats on valve seat 23, the full pumppressure is applied to the top of the diaphragm 21 thereby locking thediaphragm in a down position and applying the full pumping force of pump10 to the top or outer surface of the piston means 32. Since the pistonmeans 32 is sealed at 52 to the walls 53 of the actuator 16, the pistonmeans 32 is caused to move in a downward direction. The movement in adownward direction compresses the spring 55 and also begins to collapsethe bellows 62 which forms one wall of the reservoir chamber 35. As thebellows 62 collapses, fluid is withdrawn from the reservoir chamber 35through the pipe 36 to the pump 10. Due to the physical size of thepressure chamber 17 there is required, at this time, more fluid than theSmaller chamber 35 could supply if it were merely sealed with a singlebellows. As this volume of fluid is pumped through pump 10, the bellows66 is also caused to collapse causing an upward movement of thecup-shaped member 65 which also reduces the volume 'of the reser voirchamber 35.

With the present arrangement the collapse of the two bellows, which arein concentric relationship with one another and have a common lowersealed edge, there is provided a reservoir that is capable of supplyingall of the fluid needed for the upper or pressure chamber 17 withoutsupplying an external reservoir of any type for the present unit. Withboth bellows 62 and 66 collapsing the fluid in the lower portion of thereservoir chamber 35 is utilized even though this portion of the chamberis not occupied by the piston means 32 when it has reached its mostdownward position. The movement of the shaft 33 and the compressing ofbellows 62 compresses the spring 55. The compressed spring '55 is thereturn force utilized to cause the piston means 32 to move in an upwarddirection upon deenergization of the pump 10.

As was pointed out in connection with FIGURE 1, when pump 10 isdeenergized the spring 55 will tend to move the piston means 32 upwardslightly. This slight upward movement applies a greater pressure to theunderside of diaphragm 21 than exists on the upper side of the diaphragmsince the pump 10 no longer is the pressure source. This change inpressure allows the diaphragm to assume its normal position which opensa free fluid passage from the pressure chamber 17 through the opening 26land the valve seat 23 to the pipe 30. This allows fluid to flowdirectly back through pipe 30 and pipe 36 into the reservoir chamber 35thereby completely bypassing the limited passage of the pump channel.

The present invention has been disclosed as operable with a conductivefluid when utilized with an electromagnetic conductive fluid pump. Thedevice is considered to be hermetically sealed at all joints by anyconvenient means, as welding or soldering. It is understood that theapplicant does not wish to be limited to this arrangement solely, butwishes to be limited only by the scope of the appended claims. There aremany modifications of the present invention that would be tdaptable toVarious forms of pumps and actuators and the schematic representationalong with one preferred embodiment has been presented as an example ofone usable embodiment of the present invention.

I claim as my invention:

1. An actuating device comprising: a fluid filled chamber having aplurality of fixed rigid walls and a flexible wall; an actuating membermovably mounted within said chamber and dividing said chamber into firstand second fluid filled areas on opposite sides of said actuatingmember; means providing fluid communication be tween said first andsecond areas; means external of said chamber for causing movement ofsaid actuating member; said actuating member being in operativeengagement with one portion of said flexible wall for movement thereof;said flexible wall being deformable upon movement of said one portionthereof to maintain a constant volume in said chamber; and output meansexternal of said chamber and positioned to be movable by movement ofsaid one portion of said flexible wall.

2. In an actuating device: a fluid filled chamber comprising a fixedwall portion and sealing means including a movable wall having tworelatively movable sections; an actuating member movably mounted withinsaid chamber and dividing said chamber into first and second fluidfilled areas on opposite sides thereof; means providing fluidcommunication between said fluid filled areas; said actuating memberoperably engaging one of said sections of said movable wall for movementthereof; means external of said chamber and operable to cause movementof said actuating member; the other of said sections of said movablewall being effective upon movement of said one of said sections to moveoppositely thereto to maintain a constantvolume in said chamber; andoutput means external of said chamber and adapted to be positioned bythe movement of said one of said sections of said movable wall.

3. An actuating device comprising: a fluid filled chamber having aplurality of fixed rigid walls and a flexible wall; an actuating membermovably mounted entirely within said chamber and dividing said chamberinto first and second fluid filled areas on opposite sides of saidactuating member; means adapted to establish fluid communication betweensaid first and second areas; means external of said chamber for causingmovement of said actuating member, said actuating member being inoperative engagement with one portion of said flexible wall for movementthereof; said flexible wall being movable upon movement of said oneportion thereof to maintain a constant volume in said chamber; andoutput means external of said chamber and adapted to be positioned bymovement of said one portion of said flexible wall.

4. An actuating device comprising: a chamber having a fixed portion anda movable Wall, said movable wall having two relatively movablesections; a pressure mov able member positioned within said chamber anddividing said chamber into a pressure area and a reservoir area onopposite sides thereof, said reservoir area including said movable wall,said pressure movable member engaging one of said relatively movablesections of said mova'ble Wall for movement thereof; said chamber beingsubstantially filled with a fluid; means adapted to connect saidpressure area and said reservoir area through external fluid controlmeans; and an output member operably engaging said one of saidrelatively movable sections of said movable wall for movement therewith;said movable well being arranged so that the other of said relativelymovable sections is movable to maintain a constant volume in saidchamber regardless of the position of said one of said relativelymovable sections.

5. An actuating device comprising: a chamber having a fixed portionincluding a plurality of fixed walls and a movable portion including apair of concentric bellows rigidly and sealingly connected together atone of their ends, the other end of the outer one of said bellows beingfixed to said fixed portion; a pressure movable member positioned withinsaid chamber and dividing said chamber into a pressure area and areservoir area on opposite sides thereof, said reservoir area includingsaid movable portion, said pressure movable member engaging the otherend of the inner one of said pair of bellows for movement thereof; saidchamber being substantially filled with a fluid; means adapted toconnect said pressure area and said reservoir area through a fluid pump;and an output member operably engaging said other end of the inner oneof said bellows for movement therewith; said bellows being arranged sothat the connected ends thereof are movable to maintain a constantvolume in said chamber regardless of the position of said other end ofsaid inner one of the concentric bellows.

6. An actuator comprising: a fluid filled chamber having a fixed portionand a movable wall; said movable wall including a pair of concentricbellows rigidly connected together at one of their ends; the other endof the outer one of said bellows being fixed to said fixed portion; saidchamber including a pressure area and a reservoir area separated by amember movable in response to pressure in said pressure area; the otherend of the inner one of said pair of bellows being in operativeengagement with said pressure movable member for movement therewith andadapted for operative engagement with an output member to transmitmotion thereto; and means,

adapted to establish communication between said pressure area and saidreservoir area through external fluid control means; said bellows beingarranged so that when said other end of said inner bellows is moved inone direction relative to said chamber, the ends of said bellows whichare connected together are moved in an opposite direction thereto tomaintain a constant volume in said chamber.

References Cited in the file of this patent UNITED STATES PATENTS2,880,620 Bredtschneider Apr. 7, 1959

1. AN ACTUATING DEVICE COMPRISING: A FLUID FILLED CHAMBER HAVING APLURALITY OF FIXED RIGID WALLS AND A FLEXIBLE WALL; AN ACTAUTING MEMBERMOVABLY MOUNTED WITHIN SAID CHAMBER AND DIVIDING SAID CHAMBER INTO FIRSTAND SECOND FLUID FILLED AREAS ON OPPOSITE SIDES OF SAID ACTUATINGMEMBER; MEANS PROVIDING FLUID COMMUNICATION BETWEEN SAID FIRST ANDSECOND AREAS MEANS EXTERNAL OF SAID CHAMBER FOR CAUSING MOVEMENT OF SAIDACTUATING MEMBER; SAID ACTUATING MEMBER BEING IN OPERATIVE ENGAGEMENTWITH ONE PORTION OF SAID FLEXIBLE WALL FOR MOVEMENT THEREOF; SAIDFLEXIBLE WALL BEING DEFORMABLE UPON MOVEMENT OF SAID ONE PORTION THEREOFTO MAINTAIN A CONSTANT VOLUME IN SAID CHAMBER; AND OUTPUT MEANS EXTERNALOF SAID CHAMBER AND POSITIONED TO BE MOVABLE BY MOVEMENT OF SAID ONEPORTION OF SAID FLEXIBLE WALL.